Irrigation scheduling and winter wheat grain yield estimation under precipitation uncertainty – A case study in Badjgah area (Fars Province, Iran)

Document Type : Research Paper

Authors

Department Irrigation, Shiraz University, Shiraz, I. R. Iran

Abstract

Addressing deficit irrigation scheduling (DIS) for strategic crop production (especially wheat) under precipitation uncertainty is a priority for irrigation scheduling in drought conditions. This research investigated the precipitation uncertainty by enacting optimistic and pessimistic scenarios for the next 20 years by considering the statistical record of climate in Badjgah area. DIS was conducted in spring in two ways: (1) reducing the quantity of irrigation water at each irrigation event; (2) reducing the number of full irrigation events. Results indicated that, owing to the effect of precipitation increase on yield enhancement, grain yield in the optimistic scenario was on average 7% higher than those obtained in the pessimistic scenario. Furthermore, grain yields obtained via the second method of DIS was on average 8% higher than those obtained by the first method of DIS and further by increasing the water reduction fraction (WRF) to 0.6, this difference reached about 20% due to the effect of early spring irrigation events on yield enhancement. At low irrigation application efficiency (Ea), the difference between DIS methods was greater at higher WRF. Net income obtained through the second method of DIS was on average 70% higher than those obtained via the first method of irrigation for all conditions due to decreasing the number of irrigation events and thus decreasing the production costs. Eventually, results indicated that in both scenarios of the precipitation uncertainty in drought conditions, the second method of DIS, i. e., application of available water based on growth stage, was more fruitful.

Keywords

Main Subjects


Article Title [Persian]

برنامه بندی آبیاری و تخمین عملکرد دانه گیاه گندم زمستانه تحت شرایط عدم قطعیت آب و هوایی

Authors [Persian]

  • علیرضا سپاسخواه
  • علی اکبر کامگار حقیقی
Abstract [Persian]

پرداختن به برنامه بندی کم آبیاری محصولات استراتژیک (مخصوصاً گندم) تحت شرایط عدم قطعیت آب و هوایی در شرایط فعلی یک اولویت می باشد. ما عدم قطعیت آب و هوایی را با شبیه سازی دو سناریو خوش بینانه و بدبینانه برای 20 سال آینده بررسی کردیم که این بررسی با استفاده از داده های آماری هواشناسی ثبت شده در منطقه مورد مطالعه انجام شد. برنامه بندی کم آبیاری در فصل بهار به دو طریق انجام شد: (1) کاهش در مقدار آب آبیاری در هر یک از وقایع آبیاری. (2) کاهش تعداد وقایع آبیاری کامل. نتایج نشان دادند که به دلیل تأثیر افزایش بارندگی در افزایش عملکرد، عملکرد دانه در سناریو خوش بینانه بالاتر است. همچنین عملکردهای دانه به دست آمده در روش دوم برنامه بندی کم آبیاری بیشتر از روش اول است و با افزایش کسر کاهش آب تا 6/0، این اختلاف بیشتر می شود. این نشان می دهد که وقایع آبیاری مربوط به ابتدای فصل بهار اهمیت خیلی بیشتری نسبت به آبیاری های آخر فصل بهار دارد. در راندمان های پایین کاربرد آب در مزرعه، اختلاف قابل ملاحظه ای بین روش های برنامه بندی آبیاری در کسرهای بالاتر کاهش آب مشاهده شد. درآمد خالص به دست آمده در روش برنامه بندی کم آبیاری دوم در تمام شرایط از روش اول بیشتر بود که این به دلیل کاهش تعداد وقایع آبیاری و در نتیجه کاهش هزینه های تولید در روش دوم نسبت به روش اول می باشد. نهایتاً نتایج نشان داد که در هر دو سناریو عدم قطعیت آب و هوایی، روش دوم برنامه بندی کم آبیاری ارجح می باشد.

Keywords [Persian]

  • کسر کاهش آب
  • راندمان کاربرد آب در مزرعه
  • مدل MEDIWY
  • سناریو آب و هوایی
  • درآمد خالص
Abdollahi Ezzatabadi, M. (1996). Economic analysis of alternatives for supply of agricultural water in Rafsanjan. M.Sc. Thesis. Agricultural Economics Department (Unpublished). Shiraz University. Shiraz. I. R. Iran. 197 p.
Allen, R.G., Pereira, L.S., Raes, D., & Smith, M. (1998). Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements. FAO Irrigation and Drainage paper 56, Rome, 300 p.
Cancela, J.J., Cuesta, T.S., Neira, X.X., & Pereira, L.S. (2006). Modelling for improved irrigation water management in a temperate region of Northern Spain. Biosystems Engineering, 94(1), 151–163.
Cordery, I., & Graham, A.C. (1989). Forecasting wheat yields using a water budgeting model. Australian Journal of Agricultural Research, 40, 715-728.
English, M.J., & Raja, S.N. (1996). Every other furrows of corn irrigation. Transaction of the ASAE, 17, 426-428.
Fateh, M. (2010). Investigation of the effect of different levels of irrigation and seed rates on Shiraz cultivar wheat yield with surface irrigation in Badjgah area (Fars province). M.Sc. Thesis. Irrigation Department (Unpublished). Shiraz University. Shiraz. I. R. Iran. 145 p.
Geerts, S., Raes, D., & Garcia, M. (2010). Using AquaCrop to drive deficit irrigation schedules. Agricultural Water Management, 98, 213-216.
 Misra, S.C., Shinde, S., Geerts, S., Rao, V.S., & Monneveux, P. (2010). Can carbon isotope discrimination and ash content predict grain yield and water use efficiency in wheat? Agricultural Water Management, 97, 57-65.
Pereira, L.S., van den Broek, B., Kabat, P., & Allen, R.G. (1995). Crop–Water Simulation Models in Practice. Wageningen Press, Wageningen. 322 p
Pereira, L.S., Paredes, P., Eholpankulov, E.D., Inchenkova O.P., Teodoro, P.R., & Horst, M.G. (2009). Irrigation scheduling strategies for cotton to cope with water scarcity in the Fergana Valley, Central Asia. Agricultural Water Management, 96, 723-735.
Pereira, L.S., Oweis, T., & Zairi, A. (2002). Irrigation management under water scarcity. Agricultural Water Management, 57, 175–206.
Popova, Z., & Pereira, L.S. (2008). Irrigation scheduling for furrow-irrigated maize under climate uncertainties in the Thraceplain, Bulgarian Biosystems Engineering, 99, 587-597.
Razzaghi, F., & Sepaskhah, A.R. (2012). Calibration and validation of four common ET0 estimation equations by lysimeter data in a semi-arid environment. Archives of Agronomy and Soil Science, 58(3), 303-319.
 Rodrigues, G.C., & Pereira, L.S. (2009). Assessing economic impacts of deficit irrigation as related to water productivity and water costs. Biosystems Engineering, 103, 536-551.
Sepaskhah, A.R., Azizian, A., & Tavakoli, A.R. (2006). Optimal applied water and nitrogen for winter wheat under variable seasonal rainfall and planning scenarios for consequent crops in a semi-arid region. Agricultural Water Management, 84, 113-122.
Sepaskhah A.R., & Tafteh, A. (2012). Yield and nitrogen leaching in rapeseed field under different nitrogen rates and water saving irrigation. Agricultural Water Management, 112, 55-62.
Sepaskhah, A.R., & Akbari, D. (2005). Deficit irrigation planning under variable seasonal precipitation. Biosystems Engineering, 92(1), 97–106.
Sepaskhah, A.R., & Ghahraman, B. (2004). The Effects of Irrigation Efficiency and Uniformity Coefficient on Relative Yield and Profit for Deficit Irrigation. Biosystems Engineering, 87 (4), 495–507.
 Smith, M., Pereira, L.S., Berengena, J., Itier, B., Goussard, J., Ragab, R., Tollefson, L., & Van Hoffwegen, P. (1996). Irrigation Scheduling: From Theory to Practice. FAO Water Report 8, FAO, Rome, 384 p.
Ziaei, A.N., & Sepaskhah, A.R. (2003). Model for simulation of winter wheat yield under dryland and irrigated conditions. Agricultural Water Management, 58, 1-17.